Grandpa and I just restored a McCormick Deering horse drawn sickle mower last summer. It looks nothing like what you have there. On the sickle mower, the drive gears go through an axle tube, and a gear box. Yours has the ground engaging wheel, a big gear with a chain, then a smaller gear, turning a worm gear. All those wood slats piled up in your second picture lead me to a conveyor somewhere.